What is the primary reason for using photoelectric beams in security systems?

Using photoelectric beams in security systems is primarily for zone protection. These systems create an invisible barrier that, when interrupted by an object (like a person or vehicle), activates the security response. This feature is particularly valuable in securing specific areas or zones against unauthorized access. For example, installations around property perimeters or entry points help to alert property owners or security personnel to potential breaches before an incident occurs.

Other options, while they may involve certain functionalities, do not capture the primary purpose of photoelectric beams. Movement detection, for instance, can also be achieved through other technologies, such as motion sensors. Light intensity measurement is more relevant in contexts like automatic lighting systems rather than security. Environmental monitoring is a broader concept usually associated with sensors for temperature or humidity, which is not the main focus of photoelectric beams. Therefore, the primary function of photoelectric beams centers on providing effective zone protection for security applications.